1. Field of Invention
The invention relates, generally, to an electrical system of a vehicle and, more particularly, to such a system of a hybrid electrical and thermal vehicle that includes electrical traction.
2. Description of Related Art
The electrical system of a vehicle with hybrid electrical traction typically includes at least one electric machine (often, a synchronous alternating-current machine) that is reversible (i.e., that can work both as an electric motor by absorbing electricity and generating a mechanical motive torque and as an electrical generator by absorbing mechanical energy and generating electricity). The electric machine is also mechanically connectable to the drive wheels and controlled by a bi-directional “DC/AC” electronic-power converter (i.e., an inverter/rectifier). Furthermore, the electrical system of a hybrid-traction vehicle includes a high-voltage (and, thus, high-energy) storage system. The storage system includes a series of chemical-lithium batteries and, possibly, super-capacitors and is connected to the “DC/AC” electronic-power converter to exchange electricity with the “DC/AC” electronic-power converter itself (i.e., to supply electricity when the electric machine works as an electric motor and receive electricity when the machine works as an electric generator). Finally, the electrical system of a vehicle with hybrid traction normally includes a low-voltage [and, thus, low-energy (generally operating at 12 volts nominal)] storage system. The system includes a single chemical-lead battery supplying all auxiliary services of the vehicle that require an electrical supply and is connected to the high-voltage storage system by a mono- or bi-directional electronic “DC/DC” power converter (which adapts the voltage from the high voltage of the high-voltage storage system to the low voltage of the low-voltage storage system and replaces the traditional alternator of “thermal only” propulsion vehicles). In operation, the electronic “DC/DC” power converter transfers electricity from the high-voltage storage system to the low-voltage storage system (or, more rarely, vice versa) to supply the auxiliary services and/or recharge the low-voltage storage system.
Normally, the electronic “DC/AC” power converter that connects the high-voltage storage system to the electric machine and the electronic “DC/DC” power converter that connects the high-voltage storage system to the low-voltage storage system are housed in a same container and share the same electrical ground. Furthermore, the electronic microprocessor-control units of both converters are supplied by the low-voltage storage system because obtaining the 5 volts nominal needed for the electrical supply of the electronic microprocessor-control units is easy (i.e., cost-effective) starting from the 12 volts nominal of the low-voltage storage system while it is complex (i.e., costly) starting from the 400-600 volts nominal of the high-voltage storage system. Consequently, the container that houses the two converters is connected to the low-voltage storage system by two different electrical cables. The first two-pole electrical cable defining a large section intended to withstand the high currents (in the order of 200-300 amps) needed to supply electricity to the low-voltage storage system and/or auxiliary systems. The second two-pole electrical cable defines a small section intended to withstand the low currents (in the order of a few amps) necessary to supply electricity to all the electronic microprocessor-control units.
However, it has been observed that, in hybrid-traction vehicles having an electrical system of the type described above, electrical faults may occur that cause the melting of the electrical cable defining a small section that connects the low-voltage storage system to the electronic microprocessor units to supply electricity to the electronic microprocessor-control units themselves. Consequently, both electronic microprocessor-control units that control the converters stop working due to lack of electricity.
Thus, there is a need in the related art for an electrical system of a vehicle with electrical traction that is free from the drawbacks illustrated above. In particular, there is a need in the related art for such a system that is easy and cost-effective to implement. There is a need in the related art for such a system that is also very robust.